Aon had previously contributed up to 12% of an employee’s salary – depending on age – to the pension fund in return for a basic 2% contribution from staff, but the new arrangements will see that capped at 6%.

A spokesman said the firm was looking to “reduce fixed costs” because of challenging economic conditions. Employees will be involved in a two-month consultation on the plan.

The company’s defined benefit (final salary) pension scheme was frozen and closed to new members in 2007, the spokesman added.